Performance Chemical Dosing Application

Bronkhorst has seen a marked increase in applications for performance
chemical injection for both onshore and offshore production facilities.
These performance chemicals, such as demulsifier, biocide, scale inhibitor,
corrosion inhibitor and wax inhibitor are highly concentrated and are often
required to be injected at very low flow rates.

The traditional method of chemical injection, a piston pump with check
valves on the inlet and outlet, is tried and tested and works well for
quite long periods of time. However, on occasion the check valves can
foul and begin to “pass”. Also, out-gassing or entrained air can cause
an air-lock within the piston chamber that is simply compressed/decompressed
in situ rather than pumped. In each of these cases the pump appears to
be still working but there is no actual transfer of chemical into the pipeline.
The only way to verify actual flow has been via a graduated gauge and a
stop-watch; an empirical measurement but time consuming.

Another issue with the traditional method of injection is actually changing
the flow rate. This can only be done manually by changing the stroke length
of the piston – a process that is “trial and error” and only verifiable
using the graduated gauge as above. Fine tuning of injection rates, for
example to compensate for day/night changes in temperature, across a field
is virtually impossible as the labour required to do so is prohibitive.
This results in the injection rate being set for worst case thereby resulting
in overdosing during normal conditions – a very expensive waste.

Modern communications networks now allow for technology to arrive at
diffuse production fields. The Bronkhorst CORI-FILL
system can be installed at each injection point and real-time monitoring,
control and logging of injection rates can be achieved. This allows for
remote checking of flow rates, remote instantaneous re-setting of those
flow rates, on-board auto-alarm for status checking (for example, empty
tank alarm and pump protection shut down), density change alarm, single
point totalization, multi-point (total field) totalization for cost per
barrel calculations and pump steering signal monitoring as a guide to preventative
maintenance. In short, a very powerful tool within field management.

The technical specification is equally impressive, to mention but a
few; accuracy is +/-0.2% of Reading, the instrument is certified to ATEX
Zones 1 and 2, on-board PID control is standard, as is over-run protection
and a self-learning function, the turn-down ratio is 2000:1, flow rates
down to 0.1 grams per hour are easily achieved and the physical size (“the
smallest Coriolis instrument in the world”) is perfect for multiple injection
points within confined spaces.